Prevalence and Associations of Amblyopia in Preschool Children

Amy Shih-I Pai¹
Tien Yin Wong^2,3
Rohit Varma⁴
George Burlutsky¹
Paul Mitchell¹

¹Centre for Vision Research, Westmead Millennium Institute, University of Sydney, Sydney, Australia
²Centre for Eye Research Australia, University of Melbourne, Melbourne, Australia
³Singapore Eye Research Institute, National University of Singapore, Singapore, Singapore
⁴Doheny Eye Institute, University of Southern California, Los Angeles, CA, USA

Purpose: To determine the prevalence and associated factors of amblyopia in preschool children.

Methods: The Sydney Paediatric Eye Disease Study examined 2461 (73.8% participation) children aged between 6 and 72 months, during 2007-09. Visual acuity (VA) was assessed in children aged 30+ months using the Electronic Visual Acuity system. Unilateral amblyopia was defined as a 2-line difference in reduced VA between the two eyes, plus strabismus, anisometropia, and/or visual axis obstruction. Bilateral amblyopia was defined as bilateral reduced VA with either bilateral visual axis obstruction, or significant bilateral ametropia.

Results: 1422 children aged 30 to 72 months were included, of whom 27 (1.9%) were found to have amblyopia. Only 3 of the 27 amblyopic children had previous diagnoses or treatments. In regression analysis controlling for age, gender, and ethnicity, amblyopia was significantly associated with hyperopia (odds ratio [OR] 15.3, 95% confidence interval [CI] 6.5-36.4), astigmatism (OR 5.7, CI 2.5-12.7), anisometropia (OR 27.8, CI 11.2-69.3), and strabismus (OR 13.1, CI 4.3-40.4). There were no significant associations of amblyopia with low birthweight (<2500g), pre-term birth (<37 weeks), maternal smoking, age, gender, ethnicity, or measures of socio-economic status (p>0.05).

Conclusions: Amblyopia was found in 1.9% of this Australian preschool sample. Refractive errors, particularly hyperopia and astigmatism, in addition to anisometropia and strabismus, were the major amblyogenic factors. There was a low amblyopia detection rate in this preschool population, suggesting further work might be required to improve current vision screening strategies in preschoolers.